Some electrical circuits require an electrical resistance between the base region and emitter region of a bipolar transistor. In a vertical bipolar transistor, it is convenient to provide this resistance by simply elongating the transistor base region and placing an emitter region at one end of the base region adjacent to a first base region contact. A second base region contact is provided at the other end of the elongated base region, and an electrical shunt provided between the emitter region and the second base contact. In a vertical bipolar transistor, the isolation pocket in which the transistor is disposed forms the collector region of the transistor. Hence, an additional, i.e. collector, contact must be provided to the semi-conductor material forming the isolation pocket. In operation, the transistor emitter region is at an opposite potential from that of the collector. However, I have found that undesired electrical transients can occur in which this polarity is reversed. If the base resistor and collector contacts are adjacent to one another, there may be little resistance between them upon such polarity reversal, since their interjacent PN junction would be forwardly biased. In such event, this could provide almost a substantially direct short between these two contacts to electrical ground. If the transient has sufficient energy, this could produce permanent damage to the device.
I have found a new layout geometry for such resistor-transistor combinations in an isolated integrated circuit. It provides integral protection against such electrical transients in a compact manner.